2006/22 – Wallace Rockhole (Northern Territory) – E.coli, Hardness, Iodine, Aluminium, Turbidity, Chromium

Wallace Rockhole (Northern Territory) – E.coli

2006/07: Wallace Rockhole E.coli 3 samples exceeding trigger level. 93.8% of samples within trigger level

“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.

Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG 2011

Wallace Rockhole – Northern Territory – Hardness

2007/08: Wallace Rockhole Hardness 265mg/L

2008/09: Wallace Rockhole Hardness 265mg/L

2009/10: Wallace Rockhole Hardness 271mg/L

2010/11: Wallace Rockhole Hardness 273mg/L

2013/14: Wallace Rockhole Hardness 284mg/L

2015/16: Wallace Rockhole Hardness 289mg/L

2016/17: Wallace Rockhole Hardness 310mg/L

2021/22: Wallace Rockhole Hardness 300mg/L (av.)


“To minimise undesirable build‑up of scale in hot water systems, total hardness (as calcium
carbonate) in drinking water should not exceed 200 mg/L.

Hard water requires more soap than soft water to obtain a lather. It can also cause scale to form on hot water pipes and fittings. Hardness is caused primarily by the presence of calcium and magnesium ions, although other cations such as strontium, iron, manganese and barium can also contribute.”

Wallace Rockhole – (Northern Territory) – Iodine

2007/08: Wallace Rockhole Iodine 0.19mg/L

Iodide: Based on health considerations, the concentration of iodide in drinking water should
not exceed 0.5 mg/L.
Iodine: No guideline value has been set for molecular iodine.
The element iodine is present naturally in seawater, nitrate minerals and seaweed, mostly in the form of iodide salts. It may be present in water due to leaching from salt and mineral deposits. Iodide can be oxidised to molecular iodine with strong disinfectants such as chlorine.
Molecular iodine solutions are used as antiseptics and as sanitising agents in hospitals and laboratories.
Iodine is occasionally used for the emergency disinfection of water for field use but is not used for disinfecting larger drinking water supplies. Iodide is used in pharmaceutical and photographic materials. Iodine has a taste threshold in water of about 0.15 mg/L.
Iodide occurs in cows’ milk and seafood. Some countries add iodide to table salt to compensate for iodide-deficient diets.

Wallace Rockhole (Northern Territory) – Aluminium

2010/11: Wallace Rockhole Aluminium 0.8mg/L

2013/14: Wallace Rockhole Aluminium 0.72mg/L

According to the ADWG, no health guideline has been adopted for Aluminium, but that the issue is still open to review. Aluminium can come from natural geological sources or from the use of aluminium salts as coagulants in water treatment plants. According to the ADWG “A well-operated water filtration plant (even using aluminium as a flocculant) can achieve aluminium concentrations in the finished water of less than 0.1 mg/L.

The most common form of aluminium in water treatment plants is Aluminium Sulfate (Alum). Alum can be supplied as a bulk liquid or in granular form. It is used at water treatment plants as a coagulant to remove turbidity, microorganisms, organic matter and inorganic chemicals. If water is particularly dirty an Alum dose of as high as 500mg/L could occur. There is also concern that other metals may also exist in refined alum.

While the ADWG mentions that there is considerable evidence that Aluminium is neurotoxic and can pass the gut barrier to accumulate in the blood, leading to a condition called encephalopathy (dialysis dementia) and that Aluminium has been associated with Parkinsonism dementia and amyotrophic lateral sclerosis, the NHMRC, whilst also acknowledging studies which have linked Aluminium with Alzheimer disease, has not granted Aluminium a NOEL (No Observable Effect Level) due to insufficient and contradictory data. Without a NOEL, a health guideline cannot be established. The NHMRC has also stated that if new information comes to hand, a health guideline may be established in the future.

In communication with Aluminium expert Dr Chris Exley (Professor in Bioinorganic Chemistry
The Birchall Centre, Lennard-Jones Laboratories, Keele University, Staffordshire UK) in March 2013 regarding high levels of Aluminium detected in the South Western Victorian town of Hamilton
“It is my opinion that any value above 0.5 mg/L is totally unacceptable and a potential health risk. Where such values are maintained over days, weeks or even months, as indeed is indicated by the data you sent to me, these represent a significant health risk to all consumers. While consumers may not experience any short term health effects the result of longer term exposure to elevated levels of aluminium in potable waters may be a significant increase in the body burden of aluminium in these individuals. This artificially increased body burden will not return to ‘normal’ levels when the Al content of the potable water returns to normal but will act as a new platform level from which the Al body burden will continue to increase with age.

Wallace Rockhole (Northern Territory) – Turbidity

2010/11: Wallace Rockhole Turbidity 36.7NTU

2013/14: Wallace Rockhole Turbidity 25.7NTU

Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.

Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
consumer’s tap

Wallace Rockhole (Northern Territory) – Chromium

2016/17  – Wallace Rockhole (Northern Territory) – Chromium 0.06mg/L

2020/21  – Wallace Rockhole (Northern Territory) – Chromium 0.05mg/L

2021/22  – Wallace Rockhole (Northern Territory) – Chromium 0.04mg/L

Based on health considerations, the concentration of hexavalent chromium (Cr(VI)) in
drinking water should not exceed 0.05 mg/L. If the concentration of total chromium exceeds
this value then a separate analysis for hexavalent chromium should be undertaken.
Chromium is present in the environment in the trivalent (Cr(III)) and hexavalent (Cr(VI)) states.
Trivalent chromium is the most common naturally occurring state. Most soils and rocks contain small
amounts of chromium oxide, and weathering, oxidation and bacterial action convert this insoluble
compound into soluble Cr(III) salts.
Trivalent chromium salts are used in leather tanning, manufacture of catalysts, paint pigments, fungicides,
and ceramic and glass manufacture.
Trivalent chromium is an essential trace element for humans, with food being the major source of intake.
Hexavalent chromium occurs infrequently in nature. Its presence in water is generally the result of
industrial and domestic chromium waste discharges. Hexavalent chromium compounds are used in the
metallurgical industry for chrome alloy and chrome metal production, and in the chemical industry as
oxidising agents.
Hexavalent chromium is not considered to be an essential nutrient and harmful effects due to chromium
have been attributed to this form.
Total chromium concentrations in drinking water are usually less than 0.005 mg/L although
concentrations between 0.06 mg/L to 0.12 mg/L have been reported overseas.
In major Australian reticulated supplies concentrations of total chromium range up to 0.03 mg/L,
with typical concentrations usually less than 0.005 mg/L.